The density of rotifer Brachionus calyciflorus and the changes of environmental conditions were studied in aquarium,in which both rotifer and fish( Tilapia nilotica and Misgurnus anguillicaudatu) separated from each other were grown in medium of algae in outdoor.Results show that density of rotifer cultured with Misgurnus anguillicaudatus excesses 100 individual per ml in 11 days.There are 5 days in which rotifer densities attain 200 ind./ ml and the highest density attain 250 individual per m...